New figures released by the Department of Corrections show the number of prisoners using drugs has hit a record low.

Acting prison services assistant general manager Leanne Field said the number of prisoners returning positive results after being randomly tested had plummeted to 10.5 per cent, the lowest rate ever recorded across all prisons in New Zealand.

"This is a major achievement given that 34 per cent of prisoners tested positive when testing began in the late 1990," Mrs Field said.

She said the reduction had been achieved through ongoing investment and improvement in prison security, and enhanced visitor and prisoner searching.

"We also undertake regular searches with our 12 drug dog teams and have a highly skilled intelligence team who work to stop criminal activities within prison."

Mrs Field said getting further declines was a challenge as prisoners and their associates in the community were inventive in identifying ways to smuggle contraband into prison.

She said there was also a focus on reducing the demand for drugs in prison through treatment clinics.